From 4b7c09a5f74ad25dd2e3ee6d43732f9a0e0c1ff3 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Thu, 19 Jan 2017 16:08:49 -0500 Subject: [PATCH] nbd: only set MSG_MORE when we have more to send [ Upstream commit d61b7f972dab2a7d187c38254845546dfc8eed85 ] A user noticed that write performance was horrible over loopback and we traced it to an inversion of when we need to set MSG_MORE. It should be set when we have more bvec's to send, not when we are on the last bvec. This patch made the test go from 20 iops to 78k iops. Signed-off-by: Josef Bacik Fixes: 429a787be679 ("nbd: fix use-after-free of rq/bio in the xmit path") Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/block/nbd.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 4d30da2..42a5395 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -269,7 +269,7 @@ static inline int sock_send_bvec(struct nbd_device *nbd, struct bio_vec *bvec, static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd) { struct request *req = blk_mq_rq_from_pdu(cmd); - int result, flags; + int result; struct nbd_request request; unsigned long size = blk_rq_bytes(req); struct bio *bio; @@ -309,7 +309,6 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd) if (type != NBD_CMD_WRITE) return 0; - flags = 0; bio = req->bio; while (bio) { struct bio *next = bio->bi_next; @@ -318,9 +317,8 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd) bio_for_each_segment(bvec, bio, iter) { bool is_last = !next && bio_iter_last(bvec, iter); + int flags = is_last ? 0 : MSG_MORE; - if (is_last) - flags = MSG_MORE; dev_dbg(nbd_to_dev(nbd), "request %p: sending %d bytes data\n", cmd, bvec.bv_len); result = sock_send_bvec(nbd, &bvec, flags); -- 2.7.4